1. Field of the Invention
The present invention relates generally to wheeled vehicle steering structure alignment. More particularly, the invention relates to a tool and data base for the indexing of bushings for the adjustment of caster and/or camber in a steering structure of a wheeled vehicle, and to a method of efficiently setting the caster and camber of a vehicle steering structure using the tool and data base of the present invention.
2. Description of the Prior Art
Various rotatable adjusting bushings have been used to adjust caster and camber in wheeled vehicle steering structures. These steering structures typically include a yoke carried at an end of a front axle. At least one arm of the yoke has an opening for receiving the bushing. A wheel spindle assembly is pivotally mounted on the yoke by ball joints having a stud extending through the opening in the yoke arm, in locking engagement with the bushing. The adjusting bushing displaces the associated ball joint from the axis of exterior surface of the bushing. The orientation of the bushing within the opening determines the direction of the displacement, which is reflected as a change in the pivotal axis of the spindle and thus as changes in caster, camber or both.
Koch et al. U.S. Pat. No. 3,342,507 describes a relationship between caster and camber changes resulting from adjusting camber with an eccentric bushing. The associated king pin includes an indicating arrow or like indicia to facilitate a visual check of the camber change. The associated but undesired caster changes require additional corrective shimming elsewhere in the steering structure.
Dickerson et al. U.S. Pat. No. 4,232,880 describes an eccentric bushing having an axially offset bore. The Dickerson et al. bushing has a slot and an integral serpentine collar which facilitates manual grasping and rotation of the bushing to adjust the caster and camber of the wheel assembly. Collectively the caster and camber describe the pneumatic trail of the tire. The stud of the ball joint taught by Dickerson is threaded and may be secured by tightening an associated nut.
Drotar et al. U.S. Pat. No. 4,509,772 discloses one-piece bushings similar in structure and use to the Dickerson bushing but with the inner bore axis either angled or skewed to the axis of the outer surface cylinder. Such bushings allow a greater amount of offset than eccentric bushings. Other patents indicative of offset bushings include Mattson U.S. Pat. No. 4,026,578, Traugott U.S. Pat. No. 2,859,058 and Traugott U.S. Pat. No. 3,163,441.
With most prior art bushings, the bushing is installed and then adjusted by trial and error. Specifically, readings are taken as the bushing is rotated. This process continues until an acceptable combination of caster and camber is achieved. Finally, the ball joint stud and associated bushing are secured in the yoke. An example of this type of assembly is U.S. Pat. No. 4,400,007 to Ingalls. Once the Ingalls bushing is properly positioned, a lock ring is coincidentally fixed to the bushing and positioning lugs carried by the yoke to secure the assembly. U.S. Pat. No. 4,252,338 to Ingalls et al. describes an externally threaded bushing threaded into an internally threaded bore defined in a yoke. The Ingalls bushing may be an offset or a skewed bushing. Further, Ingalls mentions the possibility of providing a chart, graph or formula for the convenient determination of the amount of offset required and the orientation of the bushing appropriate to provide a multitude of corrective caster and/or camber settings.
Ingalls also describes a method of alignment. In the Ingalls method, misalignment is measured; a chart, graph or formula is used to select an appropriate bushing, the bushing is exchanged into the upper housing and oriented by means of an indexing mark (or a bushing slot). Finally, the assembly is secured.
Kost et al. U.S. Pat. No. 2,923,555 describes an eccentric bearing, preferably threaded, which forms the cone section of a ball joint in a steering assembly. Rotational adjustment of the eccentric bearing adjusts caster and/or camber of the steering assembly. Additionally, Kost shows a removable precalibrated scale to facilitate indexing of the bearing members when adjusting caster and/or camber. The Kost bearing includes a direction indicating mark. Kost's scale is an arctuate-shaped piece of thin, flat material which rests on top of the axle and is positioned by a pin or protrusion which fits within a slot from a split in the axle. The scale of Kost is precalibrated to the particular bearing in use.
Additionally, precalibrated scales are known in preset type adjustable offset bearings. For example, in Ingalls catalog No. 840 an adjustable bushing including an inner sleeve having an eccentric bore of an outer sleeve is disclosed. Precalibrated scales are fixed to the outer surface of each sleeve. The camber and caster provided by the bushing is set by rotating the inner sleeve with respect to the outer sleeve until selected reference symbols on each scale are aligned. Both sleeves must be circumferentially expanded, by drawing a tapered shaft of a ball joint through the inner sleeve bore, to secure the bushing in place on the yoke.
Spector et al. U.S. Pat. No. 4,641,853 describes removable scales attached to preset bushings. The scales are used on conjunction with a correlating chart to preset the bushing offset and second to preset the offset orientation which results upon installation of the bushing on the vehicle. The method includes using "splits" in the bushing as indicators and selecting from among a plurality of bushings.